1. Field of the Invention
The present invention relates to a sheet shutter which is a shutter of the type in which a sheet-form shielding material is lifted and lowered to be used as a partition of an entrance or a passage in a factory, a warehouse or the like, and more particularly to an improvement of a sheet shutter of the type in which the sheet is raised and lowered by means of a take-up drum provided in the upper part of the sheet shutter.
2. Description of the Prior Art
A sheet shutter of the type in which a sheet is raised and lowered by means of a take up drum provided in the upper part thereof, is known and disclosed in Japanese Utility Model Laid Open Publication No. 54-116953.
Such known sheet shutter has two guide rails erected parallel with a predetermined spacing therebetween, which form a part of a shutter frame, and a take-up drum provided horizontally between the upper ends of the guide rails. A flexible sheet is provided between the guide rails so as to be movable in the vertical direction along the guide rails. The sheet is attached at one end thereof on the take up drum driven by a motor. The sheet is raised and lowered by the rotation of the drum, thereby opening and closing the entrance or passage. Such a sheet shutter is structurally simple and mechanically satisfactory.
In such known sheet shutter, a motor for driving the take-up drum is placed in the front or rear side of the upper part of the shutter frame. Because of this, a large protrusion is formed on the partitioning plane of the entrance or passage, obstruction of other works and detraction from the visual appearance. In addition, when the motor is provided on the side or in the upper part of the shutter frame, there are problems, such as it inconvenience in mounting the sheet shutter at the planned position of installation and decrease in the available area in the opening and closing part due to the space taken up by the driving motor.